Brian O'Driscoll returned to inspire Leinster to a 22-16 victory over Munster at Thomond Park on Saturday night and end their Irish rivals RaboDirect PRO12 title hopes.

O'Driscoll showed his trademark poacher's instinct from a close-in ruck in the 71st minute, nipping in by the posts after a mammoth 27 phases of patient carrying and ruck control from the visitors. Munster, six days after their Heineken Cup heroics against Harlequins, tired in the closing stages at Thomond Park and Leinster, driven on by man-of-the-match Isaac Boss, got the decisive score to keep on track for a home semi-final.

The interprovincial derby afforded watching Lions coaches Warren Gatland and Rob Howley the chance to gauge the form of captaincy contenders Paul O'Connell and O'Driscoll, the latter coming back from his three-week ban. Ian Madigan's right boot was the main influence for Leinster in the first half, firing over four penalties for a 12-10 interval lead.

Joe Schmidt's men failed to take full advantage of a strong wind though, and two unconverted tries from Ian Keatley and Felix Jones in the opening period showed Munster's attacking capabilities. Keatley kicked two penalties to Madigan's one as Munster edged ahead 16-15 at the start of the second half, but in an energy-sapping end game Leinster came out on top to complete a season's double over their arch rivals.

Ulster returned to the top of the PRO12 with a 31-5 win over Newport Gwent Dragons on Friday night while previous league leaders Glasgow Warriors slipped to a 29-6 loss to the Scarlets. Ireland winger Tommy Bowe marked his return to the starting line-up after being out with injury with the opening try and Ulster then added to that with scores from the impressive Stuart Olding, Darren Cave and Paul Marshall, while Ruan Pienaar - who started at fly-half - kicked all the conversions and added a penalty for an unblemished night from the tee.

In Llanelli, the Scarlets were indebted to tries from hooker Ken Owens and Liam Williams as well as 19 points from the boot of fly-half Owen Williams. The Welsh side were 13-0 up and went in at half-time 16-6 ahead after Ruaridh Jackson had landed a brace of penalties. Williams' try early in the second half and Owen Williams' unerring accuracy with the boot kept the Scarlets comfortably ahead and Glasgow had no answer to the west Wales side, for whom Owen Williams kept the scoreboard ticking over until the final whistle.

The Ospreys complete the current play-off picture having powered to a 28-3 victory over Treviso at the Liberty Stadium. Fly-half Dan Biggar scored 18 points to lift his side back into fourth place above the Scarlets on points difference. Winger Ben John crossed for the home side's first try just before the break with Biggar soon following him over the whitewash. Scrum-half Rhys Webb crossed for the Ospreys' third and final try in the dying moments with Biggar completing the scoring with his second conversion.

Cardiff Blues regained eighth place in the table from Connacht following a comfortable 28-13 victory over Zebre in a mud-fest at the Arms Park on Saturday. Tries from outside-half Rhys Patchell, and centres Gavin Evans and Jamie Roberts, coupled with two conversions and three penalties for a 13-point haul from Six Nations Player of the Championship Leigh Halfpenny were enough to beat the Italian outfit. Bottom of the table Zebre are still searching for their first win in the league since being formed last summer but never looked likely to upset the Blues.

Elsewhere on Friday night, Connacht produced a 10-minute flourish to see off Edinburgh 32-24 in an encounter that that featured only rare flashes of flowing rugby and that was dominated by the boot. The defeat was Edinburgh's first under the three-match tenure of interim coaches Stevie Scott and Duncan Hodge. Greig Laidlaw banged over eight penalties for the hosts, while his one-time international colleague Dan Parks contributed four penalties and a drop goal, as well as the conversions of tries by Mick Kearney and Robbie Henshaw, and Gavin Duffy weighed in with one penalty.